Iris (Ιρις) Irisflower detailwas the Greek goddess of the rainbow. The Greeks used the same word for the rainbow itself, and for the plant, referring to the wide variety of flower colours found among the many species. I cannot identify this species, but I feel that such an important and widespread genus ought to have a mention on this site, and in particular its specialized flower and method of pollinization. It is worth remembering that some plants that are commonly called ‘Iris’ actually belong to other closely related genera.

The Iris genus is widely distributed throughout the northern temperate zone. The habitats are considerably varied, ranging from cold and montane regions to the grassy slopes, meadowlands and riverbanks of Europe, the Middle East and Northern Africa, Asia, and across North America. They are perennial herbs, growing from creeping rhizomes (rhizomatous irises) or, in drier climates, from bulbs (bulbous irises). They have long erect flowering stems that may be simple or branched, solid or hollow, and flattened or with a circular cross-section. The rhizomatous species usually have 3–10 basal sword-shaped leaves growing in dense clumps; the bulbous species have cylindrical basal leaves.

fruitThe inflorescences are fan-shaped and contain one or more symmetrical 6-lobed flowers. The 3 sepals, which are spreading or droop downwards, are referred to as ‘falls’. They expand from their narrow base, which in some of the rhizomatous irises has a ‘beard’ – a tuft of short upright extensions growing in its midline – into a broader expanded portion (‘limb’), often adorned with veining, lines or dots. The three (sometimes reduced) petals stand upright, partly behind the sepal bases. They are called ‘standards’. The ‘hafts’ are the top parts of the falls near the centre, where they connect to the stem. The ‘signal’ is a patch of contrasting colour surrounding the beard.

The falls form a landing pad for pollinating insects. The beard (if any) gives pollinators something to hold on to as they enter the flower. The bright lines on the falls lead into the blossom’s mouth and serve as nectar guides. As the pollinating insect enters the flower, pollen from its back (gathered from another flower) brushes off on to the outer surface of the stigmatic lip, which is receptive to pollen. After its back has collected fresh pollen from the stamen of this flower and the insect reverses out of the flower, pollen brushes against the inner surface of the stigmatic lip; but this side of the stigma is not receptive to pollen, and self-pollination is thus prevented.

The fruit is a capsule which opens up in 3 parts to reveal numerous seeds. In some species, the seeds bear an aril.